1. Field of the Invention
The invention relates to a cellular system and a method of making communication in multi-code CDMA both of which are capable of effectively using channels of a base station or base stations in multi-code CDMA (Code Division Multiple Access) communication.
2. Description of the Related Art
There have been suggested many mobile communication apparatuses or systems operating in CDMA. For instance, Japanese Unexamined Patent Publication No. 8-274687 has suggested a CDMA wireless communication system, Japanese Unexamined Patent Publication No. 9-200115 has suggested a method of controlling directivity of an antenna in a radio-station in CDMA wireless communication system, Japanese Unexamined Patent Publication No. 10-190626 has suggested a CDMA receiver, Japanese Unexamined Patent Publication No. 10-308972 has suggested a CDMA cellular system, and Japanese Unexamined Patent Publication No. 11-74820 has suggested a CDMA signal receiver.
When a mobile communication system operating in CDMA transmits data at a rate greater than a data transmission rate per one channel (one diffusion sign), it generally transmits data in multi-code transmission where it assigns a plurality of channels, that is, a plurality of diffusion signs to a user, and transmits data through a plurality of channels.
However, a conventional mobile communication system operating in multi-code CDMA is accompanied with the following two problems.
The first problem is that when high-rate communication is to be made in multi-code, if it is not possible to secure channels of a base station for all codes, the system cannot provide services to a mobile station.
The second problem is that when high-rate communication is to be made in multi-code, it would be necessary to increase the number of channels in a base station in order to provide a high connection ratio to a mobile station, resulting in that a base station could not be constructed in a small size.